Britain did not need submersible supply ships

Did Britain consider submersible supply ships like Germany's?

No. Germany needed them to evade the British blockade, while Britain was the power enforcing that blockade.

A question about submarine supply vessels highlights the asymmetry between German and British logistics. Germany needed covert carriers that could cross or evade a hostile blockade. Britain controlled the maritime blockade and retained access to surface shipping routes and overseas bases. The Royal Navy therefore had no comparable operational requirement for a submersible fleet train.